In order to improve contrast, a lattice-type black pattern, called a black matrix is generally disposed between color pixels of color filters. Chrominum is used in a conventional black matrix. In this process, chromium is deposited on an entire surface of a glass substrate and a pattern is formed through an etching process, which requires high costs and causes problems, such as high reflectivity of the chromium and environmental pollution as a result of chrome-containing waste water. For this reason, various researches have been actively carried out on a resin black matrix using a pigment dispersion method in which minute processing can be performed.
Although a research has been carried out on a method of preparing a black composition using coloring pigments other than carbon black, the coloring prigments other than the carbon black have a low light shielding property, and thus, the black composition needs to contain the coloring pigments with a high mixing ratio. As a result, there occurs a problem that viscosity of the composition increases, which makes it difficult to handle the composition or decreases strength of a formed film or adhesion of the film for a substrate.
In recent years, the importance of an LCD in the field of flat displays has been rapidly increased. The region of an LCD field, which concentrates on existing small and middle-sized mobile displays or monitors, moves to the region of large-scaled monitors or TVs. As a size of glass increases, high sensitivity needs to be ensured to reduce a process time. Since brightness needs to be improved as the result of an increase in size of a screen, a backlight having more improved brightness has been adopted. As the brightness of the backlight increases, it has been required for a black matrix to have a higher light-shielding property than that in the related art. Since the content of carbon black contained in a composition is increased in order to improve a light-shielding property, there occurs a problem that a process characteristic of the black matrix according to an increase in the content has been deteriorated. Furthermore, the large quantity of carbon contained in the composition results in a tendency to seriously deteriorate dispersion stability of the composition. As a result of the deterioration of the dispersion stability, not only process characteristics for photoresist is changed but also defects in process occur, thereby causing a reduction in productivity. A deterioration in dispersion stability causes defects such as a change in coating thickness according to a change in viscosity, the deterioration of developability, the frequent occurrence of residues, projections, which are directly linked with productivity. Accordingly, it has become a major development issue to develop a black matrix photoresist composition, which can maintain the dispersion stability of a composition while securing a high light-shielding property, has improved adhesion to substrates and a wide development process margin, and can improve photosensitivity, as required by related companies.